C programming complete the code for the removeItem() function in the program bel

Question

C programming

complete the code for the removeItem() function in the program below. Be sure to update both the prev and next pointers where necessary.

#include <stdio.h>

struct dLink {
    struct dLink *prev;
    int value;
    struct dLink *next;
};

// print the linked list
void printList(struct dLink *head) {
    struct dLink *ptr = head;

    printf("head pointer: %p ", head);

    while (ptr != NULL) {
        printf("item address: %p ", ptr);
        printf("prev pointer: %p ", ptr->prev);
        printf("       value: %d ", ptr->value);
        printf("next pointer: %p ", ptr->next);
        ptr = ptr->next;
    }
}

// append a new entry to the end of the doubly linked list
struct dLink * appendEntry(struct dLink *head, struct dLink *newItem) {
    // empty list, the new item becomes the head
    if (head == NULL) {
        head = newItem;
    }
    // non-empty list
    else {
        struct dLink *ptr = head;

        // find the last item in the list
        while(ptr->next != NULL) {
            ptr = ptr->next;
        }

        ptr->next = newItem; // update ptr's next pointer
        newItem->prev = ptr; // update newItems's prev pointer
    }

    return head;
}

// Problem 1: insert the new item into the linked list after the item pointed to by afterItem
struct dLink * insertEntryAfter(struct dLink *head, struct dLink *afterItem, struct dLink *newItem) {
    // TODO

    return head;
}

// Problem 2: insert the new item into the linked list before the item pointed to by beforeItem
struct dLink * insertEntryBefore(struct dLink *head, struct dLink *beforeItem, struct dLink *newItem) {
    // TODO

    return head;
}

// Problem 3: remove the item pointed to by removeItem from the linked list
struct dLink * removeItem(struct dLink *head, struct dLink *removeItem) {
    // TODO

    return head;
}

int main(void) {
    struct dLink *head = NULL;

    struct dLink a = {NULL, 100, NULL};
    head = appendEntry(head, &a);

    struct dLink b = {NULL, 200, NULL};
    head = appendEntry(head, &b);

    struct dLink c = {NULL, 300, NULL};
    head = appendEntry(head, &c);

    struct dLink d = {NULL, 400, NULL};
    head = appendEntry(head, &d);

    struct dLink e = {NULL, 500, NULL};
    head = appendEntry(head, &e);

    // test solution to Problem 3
    head = removeItem(head, &a);

    // test solution to Problem 3
    head = removeItem(head, &c);

    // test solution to Problem 3
    head = removeItem(head, &e);

    printList(head);

    return 0;
}

Explanation / Answer

#include <stdio.h>

struct dLink {
    struct dLink *prev;
    int value;
    struct dLink *next;
};

// print the linked list
void printList(struct dLink *head) {
    struct dLink *ptr = head;

    printf("head pointer: %p ", head);

    while (ptr != NULL) {
        printf("item address: %p ", ptr);
        printf("prev pointer: %p ", ptr->prev);
        printf("       value: %d ", ptr->value);
        printf("next pointer: %p ", ptr->next);
        ptr = ptr->next;
    }
}

// append a new entry to the end of the doubly linked list
struct dLink * appendEntry(struct dLink *head, struct dLink *newItem) {
    // empty list, the new item becomes the head
    if (head == NULL) {
        head = newItem;
    }
    // non-empty list
    else {
        struct dLink *ptr = head;

        // find the last item in the list
        while(ptr->next != NULL) {
            ptr = ptr->next;
        }

        ptr->next = newItem; // update ptr's next pointer
        newItem->prev = ptr; // update newItems's prev pointer
    }

    return head;
}

struct dLink * insertEntryAfter(struct dLink *head, struct dLink *afterItem, struct dLink *newItem) {

return head;

}

struct dLink * insertEntryBefore(struct dLink *head, struct dLink *beforeItem, struct dLink *newItem)

{

return head;

}

struct dLink * removeItem(struct dLink *head, struct dLink *removeItem) { return head;

}

int main(void) {
    struct dLink *head = NULL;

    struct dLink a = {NULL, 100, NULL};
    head = appendEntry(head, &a);

    struct dLink b = {NULL, 200, NULL};
    head = appendEntry(head, &b);

    struct dLink c = {NULL, 300, NULL};
    head = appendEntry(head, &c);

    struct dLink d = {NULL, 400, NULL};
    head = appendEntry(head, &d);

    struct dLink e = {NULL, 500, NULL};
    head = appendEntry(head, &e);

head = removeItem(head, &a);

  
    head = removeItem(head, &c);

    head = removeItem(head, &e);

    printList(head);

    return 0;
}

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